CN112753180A - Systems and methods for NR V2X CSI feedback without using a dedicated reference signal - Google Patents

Abstract

A User Equipment (UE) configured for multi-antenna communication, the UE estimating at least one of a rank indicator and a channel quality indicator of D2D based on communication data associated with a plurality of packets transmitted using device-to-device (D2D) communication and without using a dedicated reference signal for D2D communication. The UE may be configured to operate as at least one of a transmitter (Tx) and a receiver (Rx) for vehicle-to-all (V2X) communications over a sidelink channel.

Description

Systems and methods for NR V2X CSI feedback without using a dedicated reference signal

Cross Reference to Related Applications

This patent application claims the benefit of provisional patent application No.62/739,047 filed on 28.9.2018, which is hereby incorporated by reference in its entirety.

Technical Field

The present application relates generally to wireless communication systems, and more particularly to device-to-device (D2D) communication.

Background

Wireless mobile communication technology uses various standards and protocols to transfer data between base stations and wireless mobile devices. Wireless communication system standards and protocols may include third generation partnership project (3GPP) Long Term Evolution (LTE); the Institute of Electrical and Electronics Engineers (IEEE)802.16 standard, which is commonly referred to by industry organizations as Worldwide Interoperability for Microwave Access (WiMAX); and the IEEE 802.11 standard for Wireless Local Area Networks (WLANs), which is commonly referred to by industry organizations as Wi-Fi. In a 3GPP Radio Access Network (RAN) in an LTE system, a base station, which may include a RAN node such as an evolved universal terrestrial radio access network (E-UTRAN) node B (also commonly denoted as evolved node B, enhanced node B, eNodeB, or eNB) and/or a Radio Network Controller (RNC) in the E-UTRAN, communicates with a wireless communication device known as a User Equipment (UE). In a fifth generation (5G) wireless RAN, the RAN node may comprise a 5G node, a New Radio (NR) node, or a gdnodeb (gnb).

The RAN communicates between the RAN node and the UE using a Radio Access Technology (RAT). The RAN may include global system for mobile communications (GSM), enhanced data rates for GSM evolution (EDGE) RAN (geran), Universal Terrestrial Radio Access Network (UTRAN), and/or E-UTRAN, which provide access to communication services through a core network. Each of the RANs operates according to a particular 3GPP RAT. For example, GERAN implements a GSM and/or EDGE RAT, UTRAN implements a Universal Mobile Telecommunications System (UMTS) RAT or other 3GPP RAT, and E-UTRAN implements an LTE RAT.

The core network may be connected to the UE through the RAN node. The core network may include a Serving Gateway (SGW), a Packet Data Network (PDN) gateway (PGW), an Access Network Detection and Selection Function (ANDSF) server, an enhanced packet data gateway (ePDG), and/or a Mobility Management Entity (MME).

Drawings

Fig. 1 and 2 show graphs showing BLER versus SNR for various feedback scenarios.

Fig. 3 is a flow diagram of a method for a UE configured for multi-antenna D2D communication, according to one embodiment.

Fig. 4 is a flowchart of a method for using HARQ information according to one embodiment.

Fig. 5 is a flowchart of a method for estimating a channel quality indicator based on a DMRS according to one embodiment.

Fig. 6 is a flow diagram of a method for determining a rank indicator based on long term channel statistics according to one embodiment.

Fig. 7 is a flow diagram of a method for determining a rank indicator based on precoder cycling according to one embodiment.

Fig. 8 shows a system according to an embodiment.

Fig. 9 shows an apparatus according to an embodiment.

FIG. 10 illustrates an exemplary interface according to one embodiment.

Fig. 11 shows a system according to an embodiment.

Fig. 12 illustrates a component according to one embodiment.

Detailed Description

In order to efficiently and effectively use multi-antenna techniques (e.g., multiple-input multiple-output (MIMO)) for advanced vehicle-to-all (V2X) communications, a transmitter (Tx) UE obtains information about the propagation channel, i.e., Channel State Information (CSI), Channel Quality Indicator (CQI), and/or Rank Indicator (RI) for the design and/or selection of the correct precoding matrix. This is particularly useful for unicast and multicast transmission modes, where overall performance can be improved if MIMO with precoding is employed. Typically, cellular systems employ specific or dedicated Reference Signal (RS) based CSI feedback in the downlink and uplink. For example, for the NR downlink air interface, the CSI-RS is transmitted by the gNB and the UE reports one or several of the following indicators: RI, Precoding Matrix Indicator (PMI) or CQI, CSI Resource Index (CRI), and/or Layer Indicator (LI) for Phase Tracking Reference Signal (PTRS), depending on network configuration. The feedback is periodic or aperiodic. However, this method has a problem if the closed-loop MIMO method is adopted in the eV2X sidelink. For example, even for low to medium vehicle speeds, the CSI expires quickly, making the feedback almost useless. Furthermore, RS causes additional overhead, which reduces the overall spectral efficiency.

Generally, PMIs expire very quickly, as they depend mainly on the instantaneous implementation of the channel. This is shown, for example, in an evaluation of the graphs shown in fig. 1 and 2, which show the block error rate (BLER) versus the signal-to-noise ratio (SNR) in decibels (dB) for various feedback scenarios.

FIG. 1 shows a graph 100 of line-of-sight (LOS) operation, where the graph on the left corresponds to a vehicle speed of zero (0) kilometers per hour (km/h) and the graph on the right corresponds to a relative vehicle speed of 30 km/h.

Similarly, FIG. 2 shows a graph 200 of non line of sight (NLOS) operation, where the graph on the left corresponds to a vehicle speed of 0km/h and the graph on the right corresponds to a relative vehicle speed of 30 km/h.

According to 3GPP TS 38.214, the minimum delay between transmitting the RS for PMI estimation and applying the feedback information at the transmitter, including the time slots needed for transmitting the feedback, the calculation of CSI, is three time slots. Furthermore, since the PMI is changing, the PMI needs to be transmitted periodically. In the legend of fig. 1 and 2, the acronyms DzPy (e.g., D3P5, D3P10, and D3P20) represent a delay of z slots and a periodicity of y slots. In the examples shown in fig. 1 and 2, Narrowband (NB) and Wideband (WB) feedback and precoder Cycling (CPMI) were evaluated. The examples show that the performance of open loop PMI loop already exceeds the performance of closed loop PMI feedback even for very moderate relative velocities of 30 km/h.

Thus, in accordance with certain embodiments herein, various methods are disclosed for correctly obtaining transmitter side channel state information (Tx-CSI) to improve D2D communication, such as sidelink enhanced V2X (eV2X) performance when employing MIMO technology (i.e., multiple Tx and Rx antennas).

The existing LTE-V2X sidelink physical layer specification assumes the use of only broadcast communication mode. In this case, any channel adaptation may not be applicable, as it may not be practical to gain knowledge of all channels. For example, it is impractical to employ channel dependent MIMO precoding, since it is generally not possible to find an optimal solution for many different links between a Tx UE and multiple Rx UEs.

In the downlink and uplink of NR, CSI-RS and Sounding Reference Signals (SRS) are used for channel sounding to potentially report an indicator to the other side, which may be, for example, a particular precoding matrix. This is the so-called closed loop MIMO method.

Another alternative solution is to apply channel reciprocity. In this case, CSI is also obtained in the reverse link based on the RS used for channel sounding, i.e., CSI is obtained at reception, and a reciprocal channel is assumed for transmission, since the same channel and bandwidth are used for Tx and Rx in this case.

The disadvantages of the previous solutions include: feedback of CSI may expire quickly due to high mobility; CSI-RS and SRS, or any particular RS used for channel sounding, means increased overhead, i.e. reduced overall spectral efficiency; and the reciprocity approach limits the implementation options for the configuration and antenna allocation of the automotive company. For example, in some implementations, the vehicle may use different sets of antennas for Tx and Rx. Furthermore, correct calibration may be required, which implies additional overhead, complexity and increased delay.

Accordingly, certain embodiments disclosed herein obtain Tx-CSI suitable for NR D2D communications, such as sidelink V2X communications. Such embodiments provide reduced CSI RS overhead for V2X service, flexible implementation of antenna configuration, and adaptation to long term parameters of the system rather than instantaneous implementation. To achieve this performance, some embodiments determine the CQI and RI from other existing RSs that are reused for demodulation and/or synchronization. In addition or in other embodiments, a precoding cycle is used for RI estimation and reporting.

Certain embodiments disclosed herein provide: significant improvement in V2V demodulation performance for future cellular-V2X systems supporting advanced use cases; significant improvements in spectral efficiency and reliability of future cellular-V2X communications to improve advanced security and non-security related use cases; modem to improve vehicle Telematics Control Unit (TCU) used in the automotive industry; and/or to provide optimized communication standards to facilitate rapid adoption of the system.

As described above, the evaluations shown in fig. 1 and 2 conclude that PMI feedback may not provide gain even under knowledge of the ideal channel at the receiver, even in relatively slow fading scenarios with a relative moving speed of 30km/h between Tx and Rx. Since it is often beneficial to adjust the transmission rank and modulation coding format to optimize resource utilization and provide sufficient reliability, these parameters may need to be known at the transmitter. The inventors herein realized through PMI simulations that the instantaneous implementation of the channel is changing rapidly, but as shown by the simulation assumptions in ICT-619555 resume, "D4.3 Report on channel analysis and modification", aug.2015 and 3GPP TR 37.885, large-scale parameters remain constant over a large area. At a minimum, the region in which the large scale parameters are similar is in the range of about 7 meters (m) to about 10 m. Further, it should be appreciated that one of the applications for unicast and multicast would be queuing, where vehicles travel in the same direction at similar distances. Thus, large-scale parameters remain coherent for even longer. Thus, for NR V2X there is a benefit of accommodating large scale parameters.

In the next step, the transmitter may acquire channel information according to the large-scale parameters. This is different from the uplink and downlink cases, where the feedback is based only on the instantaneous implementation of the channel. Since certain embodiments adapt to longer term parameters of the system, it may be considered a large overhead considering dedicated reference signals, since these reference signals need to be transmitted periodically. Since averaging may be performed over multiple realizations, this is a larger overhead than in the uplink and downlink. Thus, certain embodiments herein provide for estimating these parameters of the system using other signals transmitted during the continuous exchange of information.

In accordance with the current assumptions of the NR V2X research project, it is assumed herein that handshaking is also used to exchange preliminary information about channel quality in some embodiments. Thereafter, during the continuous exchange of data, CQI and RI are estimated by each device, and feedback is sent to the other participating transmitters. In various embodiments described below, the CQI is adaptive according to outer loop link adaptation, the CQI is based on long term channel statistics, the RI is based on long term channel statistics, and/or the RI is based on precoder cycling without PMI feedback.

CQI adaptive according to outer loop link adaptation

In one embodiment, outer loop link adaptation is employed based on hybrid automatic repeat request (HARQ). The CQI may then be derived based on an Acknowledgement (ACK) response and a Negative Acknowledgement (NACK) response. In this case, if a modulation coding scheme is selected and the amount of NACK increases within a period of time, the bits per symbol may be decreased. In a similar manner, if no NACK response occurs or the NACK response decreases over a period of time, the spectral efficiency may be too small and the bits per symbol may increase. This adjustment may occur in the transmitter itself, as it would require feedback of this information to initiate the retransmission, or it may be part of the feedback from the receiver to the transmitter. Furthermore, in some embodiments, the adaptation may be a gradual process, where the modulation coding scheme is only readjusted once every X received ACK/NACK responses. For example, the modulation coding scheme may be adjusted every ten received ACK/NACK responses.

Additionally or in other embodiments, the outer loop may take into account overall load and interference measurements in the environment. Considering that the vehicular UE may always be expected to perform sensing and reception from other UEs, the vehicular UE is expected to be well aware of radio environment conditions.

Cqi based on long term channel statistics

In one implementation, the CQI may be based on long-term channel statistics. The receiver typically estimates the channel based on a demodulation reference signal (DMRS) to demodulate the transmission. This information can be used to calculate CQI based on long-term statistics of the estimated channel. The CQI based on the long-term statistics of the channel may then be reported to the transmitter. DMRS may also be used, for example, to measure the interference level per subchannel (e.g., per Physical Resource Block (PRB)). Both channel and interference measurements may be averaged or weighted, e.g., over a particular time period and/or transmission bandwidth, and used for CQI estimation.

RI based on long-term channel statistics

In one embodiment, the RI may also be estimated based on long-term channel statistics. For example, DMRS may also be the basis for RI estimation. In some such embodiments, if channel coefficients received at different receive antennas at the same subcarrier and Orthogonal Frequency Division Multiplexing (OFDM) symbol are highly correlated, the channel has rank deficiency and cannot support multiple spatial layers. However, if the channel coefficients are only weakly correlated, multiple spatial layers may be supported. In some embodiments, the estimate of correlation may be an average of multiple receptions, and may then be fed back to the transmitter.

In addition or in other embodiments, precoder cycling may also enable MIMO channel measurements if the precoder consists of a single matrix or emulates TX antenna selection. Thus, knowledge of the MIMO channel can be derived from the DMRS signals and used for RI detection and feedback.

RI based on precoder cycling without PMI feedback

In one embodiment, the RI may be based on precoder cycling without PMI feedback. As described above, PMI feedback may not provide a benefit to the system. Therefore, to increase diversity, precoder cycling should be used. The devices may, for example, exchange information about the codebook used and which portion of the codebook was used during the initial handshake or internally within the accompanying control information during each transmission. With information on the precoding matrix used, the receiver can estimate the channel, e.g., without precoding from a DRMS-based channel estimation used for demodulation. From the precoding matrix information, the rank of the channel may for example be estimated and fed back to the transmitter.

Exemplary method

Fig. 3 is a flow diagram of a method 300 for a UE configured for multi-antenna D2D communication, according to one embodiment. The UE may be configured, for example, as a transmitter (Tx) and/or a receiver (Rx) for V2X communications over, for example, a sidelink channel. In block 302, the method 300 estimates at least one of a rank indicator and a channel quality indicator for a sidelink channel based on communication data associated with a plurality of packets transmitted over the sidelink channel and without using a dedicated reference signal for the sidelink channel. In block 304, the method 300 encodes a feedback message to one or more transmitters engaged in communication using the sidelink channel, the feedback message indicating at least one of a rank indicator and a channel quality indicator.

In certain embodiments, the communication data includes HARQ information including ACK responses and NACK responses associated with a plurality of packets transmitted over the sidelink channel. For example, fig. 4 is a flow diagram of a method 400 for using HARQ information, according to one embodiment. In block 402, the method 400 monitors the ACK response and the NACK response for the selected modulation coding scheme. In block 404, if the NACK response increases over a period of time, the method 400 adjusts the modulation coding scheme to reduce the number of bits per symbol. In block 406, if the NACK response decreases by or below the threshold number within the time period, the method 400 adjusts the modulation coding scheme to increase the number of bits per symbol. In block 408, the method 400 encodes the feedback message to include an indication of the adjustment to the modulation coding scheme.

In certain embodiments, the communication data includes demodulation information associated with demodulation of a plurality of packets received at the UE over the sidelink channel over a time period. For example, the demodulation information may include DMRS. Fig. 5 is a flow diagram of a method 500 for estimating a channel quality indicator based on a DMRS, according to one embodiment. In block 502, the method 500 determines an estimated channel to demodulate a plurality of packets transmitted over a sidelink channel based on a DMRS. In block 504, the method 500 calculates a channel quality indicator based on long-term statistics of the estimated channel. In certain such embodiments, the method 500 determines (in block 506) an interference measurement for each Physical Resource Block (PRB) based on the DMRS and determines (in block 508) a channel quality indicator by averaging or weighting both the estimated channel and interference measurements over the time period.

In certain embodiments, the rank indicator may also be estimated based on DMRS or other long term channel statistics. For example, fig. 6 is a flow diagram of a method 600 for determining a rank indicator based on long term channel statistics, according to one embodiment. In block 602, if the channel coefficients received at different receive antennas of the UE corresponding to the same subcarriers and OFDM symbols are highly correlated, the method 600 configures the UE to use a single spatial layer for the sidelink channel. In block 604, if the channel coefficients are weakly correlated, the method 600 configures the UE to use multiple spatial layers for the sidelink channel.

Fig. 7 is a flow diagram of a method 700 for determining a rank indicator based on precoder cycling. In block 702, the method 700 exchanges codebook information with one or more transmitters or receivers in communication with the UE over the sidelink channel. The codebook information indicates a cycle of precoders for a plurality of packets. In block 704, the method 700 estimates a MIMO channel based on the cycle of precoders. In block 706, the method 700 determines a rank indicator based on the MIMO channel.

Exemplary systems and devices

Fig. 8 illustrates an architecture of a system 800 of a network according to some embodiments. System 800 is shown to include UE 802; a 5G access node or RAN node (shown as (R) AN node 808); user plane functions (shown as UPF 804); a data network (DN 806), which may be, for example, an operator service, internet access, or 3 rd party service; and a 5G core network (5GC) (shown as CN 810).

CN 810 may include an authentication server function (AUSF 814); core access and mobility management functions (AMF 812); a session management function (SMF 818); a network exposure function (NEF 816); a policy control function (PCF 822); a Network Function (NF) repository function (NRF 820); unified data management (UDM 824); and an application function (AF 826). CN 810 may also include other elements not shown, such as a structured data storage network function (SDSF), an unstructured data storage network function (UDSF), and so forth.

The UPF 804 may serve as an anchor point for intra-RAT and inter-RAT mobility, an external PDU session point interconnecting to the DN 806, and a branch point to support multi-homed PDU sessions. The UPF 804 may also perform packet routing and forwarding, packet inspection, enforcement of the user plane portion of policy rules, lawful interception of packets (UP collection); traffic usage reporting, performing QoS processing on the user plane (e.g., packet filtering, gating, UL/DL rate enforcement), performing uplink traffic verification (e.g., SDF to QoS flow mapping), transmit level packet marking in uplink and downlink, and downlink packet buffering and downlink data notification triggering. The UPF 804 may include an uplink classifier to support routing of traffic flows to a data network. DN 806 may represent various network operator services, internet access, or third party services.

The AUSF 814 may store data for authentication of the UE 802 and handle functions related to authentication. AUSF 814 may facilitate a common authentication framework for various access types.

The AMF 812 may be responsible for registration management (e.g., responsible for registering the UE 802, etc.), connection management, reachability management, mobility management, and lawful interception of AMF-related events, as well as access authentication and authorization. AMF 812 may provide transport for SM messages of SMF 818 and act as a transparent proxy for routing SM messages. The AMF 812 may also provide transport for Short Message Service (SMS) messages between the UE 802 and an SMS function (SMSF) (not shown in fig. 8). The AMF 812 may serve as a security anchor function (SEAF), which may include interactions with the AUSF 814 and the UE 802, receiving intermediate keys established as a result of the UE 802 authentication process. In the case where USIM-based authentication is used, the AMF 812 may retrieve security materials from the AUSF 814. The AMF 812 may also include a Secure Content Management (SCM) function that receives keys from the SEA for deriving access network-specific keys. Further, the AMF 812 may be a termination point of a RAN CP interface (N2 reference point), a termination point of NAS (ni) signaling, and performs NAS ciphering and integrity protection.

The AMF 812 may also support NAS signaling with the UE 802 through an N3 interworking function (IWF) interface. An N3IWF may be used to provide access to untrusted entities. The N3IWF may be the endpoint of the N2 and N3 interfaces for the control plane and user plane, respectively, and thus may handle N2 signaling for PDU sessions and QoS from SMF and AMF, encapsulate/decapsulate packets for IPSec and N3 tunnels, label N3 user plane packets in the uplink, and enforce QoS corresponding to N3 packet labeling in view of QoS requirements associated with such labeling received over N2. The N3IWF may also relay uplink and downlink control plane nas (ni) signaling between the UE 802 and the AMF 812, and uplink and downlink user plane packets between the UE 802 and the UPF 804. The N3IWF also provides a mechanism for establishing an IPsec tunnel with the UE 802.

SMF 818 may be responsible for session management (e.g., session establishment, modification, and publication, including tunnel maintenance between UPF and AN nodes); UE IP address assignment & management (including optional authorization); selection and control of the UP function; configuring traffic steering at the UPF to route traffic to the correct destination; terminating the interface towards the policy control function; a policy enforcement and QoS control part; lawful interception (for SM events and interface with LI system); terminate the SM portion of the NAS message; a downlink data notification; initiator of AN specific SM message sent to AN through N2 via AMF; the SSC pattern for the session is determined. SMF 818 may include the following roaming functions: processing local execution to apply QoS SLA (VPLMN); a charging data acquisition and charging interface (VPLMN); lawful interception (in VPLMN for SM events and interfaces to LI systems); interaction with the foreign DN is supported to transmit signaling for PDU session authorization/authentication through the foreign DN.

NEF 816 may provide a means for securely exposing services and capabilities provided by 3GPP network functions for third parties, internal exposure/re-exposure, application functions (e.g., AF 826), edge computing or fog computing systems, and the like. In such embodiments, NEF 816 may authenticate, authorize, and/or limit AF. NEF 816 may also translate information exchanged with AF 826 and information exchanged with internal network functions. For example, NEF 816 may translate between AF service identifiers and internal 5GC information. NEF 816 may also receive information from other Network Functions (NFs) based on their exposed capabilities. This information may be stored as structured data at NEF 816 or at data store NF using a standardized interface. The stored information may then be re-exposed to other NFs and AFs by NEF 816 and/or used for other purposes such as analysis.

NRF 820 may support a service discovery function, receive NF discovery requests from NF instances, and provide information of discovered NF instances to NF instances. NRF 820 also maintains information on available NF instances and the services these instances support.

PCF 822 may provide policy rules for control plane functions to perform these functions and may also support a unified policy framework for managing network behavior. PCF 822 may also implement a Front End (FE) to access subscription information related to policy decisions in the UDR of UDM 824.

UDM 824 may process subscription-related information to support processing of communication sessions by network entities, and may store subscription data for UE 802. The UDM 824 may include two parts: an application FE and a User Data Repository (UDR). The UDM may include a UDM FE that is responsible for handling credentials, location management, subscription management, and the like. Several different front ends may serve the same user in different transactions. The UDM-FE accesses the subscription information stored in the UDR and executes authentication credential processing; processing user identification; access authorization; registration/mobility management; and subscription management. The UDR may interact with PCF 822. UDM 824 may also support SMS management, where an SMS-FE implements similar application logic previously discussed.

The AF 826 may provide application impact on traffic routing, access Network Capability Exposure (NCE), and interact with the policy framework for policy control. The NCE may be a mechanism that allows 5GC and AF 826 to provide information to each other via NEF 816, which may be used for edge computation implementations. In such implementations, network operator and third party services may be hosted near the UE 802 access point of the accessory to enable efficient service delivery with reduced end-to-end delay and load on the transport network. For edge computation implementations, the 5GC may select a UPF 804 near the UE 802 and perform traffic steering from the UPF 804 to the DN 806 via the N6 interface. This may be based on the UE subscription data, UE location and information provided by the AF 826. As such, the AF 826 may affect UPF (re) selection and traffic routing. Based on operator deployment, the network operator may allow AF 826 to interact directly with the relevant NFs when AF 826 is considered a trusted entity.

As discussed previously, CN 810 may include an SMSF, which may be responsible for SMS subscription checking and verification and relaying SM messages to and from UE 802 from and to other entities, such as SMS-GMSC/IWMSC/SMS routers. The SMS may also interact with the AMF 812 and UDM 824 for notification procedures that the UE 802 is available for SMS transmission (e.g., set a UE unreachable flag, and notify the UDM 824 when the UE 802 is available for SMS).

The system 800 may include the following service-based interfaces: namf: service-based interfaces presented by the AMF; nsmf: SMF-rendered service-based interfaces; nnef: NEF-presented service-based interface; npcf: a service-based interface presented by the PCF; nudm: UDM rendered service-based interfaces; naf: a service-based interface for AF presentation; nnrf: NRF rendered service-based interfaces; and Nausf: AUSF-presented service-based interface.

The system 800 may include the following reference points: n1: a reference point between the UE and the AMF; n2: (R) a reference point between AN and AMF; n3: (R) a reference point between AN and UPF; n4: a reference point between SMF and UPF; and N6: reference point between the UPF and the data network. There may be more reference points and/or service-based interfaces between NF services in these NFs, however these interfaces and reference points are omitted for clarity. For example, the NS reference point may be between the PCF and the AF; the N7 reference point may be between the PCF and the SMF; the N11 reference point may be between AMF and SMF, etc.; in some embodiments, CN 810 may include an Nx interface, which is an inter-CN interface between MME and AMF 812 to enable interworking between CN 810 and other core networks.

Although not shown in fig. 8, the system 800 may include a plurality of RAN nodes, such as (R) AN nodes 808, wherein AN Xn interface is defined between two or more (R) AN nodes 808 (e.g., gnbs, etc.) connected to the 5GC 410, between AN (R) AN node 808 (e.g., gNB) connected to the CN 810 and AN eNB, and/or between two enbs connected to the CN 810.

In some implementations, the Xn interface can include an Xn user plane (Xn-U) interface and an Xn control plane (Xn-C) interface. The Xn-U may provide non-guaranteed delivery of user plane PDUs and support/provide data forwarding and flow control functions. The Xn-C can provide management and error processing functions for managing the functions of the Xn-C interface; mobility support for the UE 802 in connected mode (e.g., CM connected) includes functionality for managing connected mode UE mobility between one or more (R) AN nodes 808. The mobility support may include context transfer from the old (source) serving (R) AN node 808 to the new (target) serving (R) AN node 808; and control of the user plane tunnel between the old (source) serving (R) AN node 808 to the new (target) serving (R) AN node 808.

The protocol stack of the Xn-U may include a transport network layer established on top of an Internet Protocol (IP) transport layer, and a GTP-U layer on top of UDP and/or IP layers for carrying user plane PDUs. The Xn-C protocol stack may include an application layer signaling protocol, referred to as the Xn application protocol (Xn-AP), and a transport network layer built on top of the SCTP layer. The SCTP layer can be located on top of the IP layer. The SCTP layer provides guaranteed delivery of application layer messages. In the transport IP layer, point-to-point transport is used to deliver the signaling PDUs. In other implementations, the Xn-U protocol stack and/or the Xn-C protocol stack may be the same as or similar to the user plane and/or control plane protocol stacks shown and described herein.

Fig. 9 illustrates example components of a device 900 according to some embodiments. In some embodiments, device 900 may include application circuitry 902, baseband circuitry 904, Radio Frequency (RF) circuitry (shown as RF circuitry 920), Front End Module (FEM) circuitry (shown as FEM circuitry 930), one or more antennas 932, and Power Management Circuitry (PMC) (shown as PMC 934) coupled together at least as shown. The components of exemplary apparatus 900 may be included in a UE or RAN node. In some embodiments, the apparatus 900 may include fewer elements (e.g., the RAN node may not utilize the application circuitry 902, but rather includes a processor/controller to process IP data received from the EPC). In some embodiments, device 900 may include additional elements, such as memory/storage, a display, a camera, a sensor, or an input/output (I/O) interface. In other embodiments, the following components may be included in more than one device (e.g., the circuitry may be included separately in more than one device for cloud-RAN (C-RAN) implementations).

The application circuitry 902 may include one or more application processors. For example, the application circuitry 902 may include circuitry such as, but not limited to, one or more single-core or multi-core processors. The one or more processors may include any combination of general-purpose processors and special-purpose processors (e.g., graphics processors, application processors, etc.). The processors may be coupled to or may include memory/storage and may be configured to execute instructions stored therein to enable various applications or operating systems to run on device 900. In some embodiments, the processor of the application circuitry 902 may process IP data packets received from the EPC.

Baseband circuitry 904 may include circuitry such as, but not limited to, one or more single-core or multi-core processors. Baseband circuitry 904 may include one or more baseband processors or control logic components to process baseband signals received from the receive signal path of RF circuitry 920 and to generate baseband signals for the transmit signal path of RF circuitry 920. Baseband circuitry 904 may interact with application circuitry 902 to generate and process baseband signals and to control the operation of RF circuitry 920. For example, in some embodiments, the baseband circuitry 904 may include a third generation (3G) baseband processor (3G baseband processor 906), a fourth generation (4G) baseband processor (4G baseband processor 908), a fifth generation (5G) baseband processor (5G baseband processor 910), or other existing generations, other baseband processors 912 of generations that are being developed or are to be developed in the future (e.g., second generation (2G), sixth generation (6G), etc.). The baseband circuitry 904 (e.g., one or more of the baseband processors) may process various radio control functions that enable communication with one or more radio networks via the RF circuitry 920. In other embodiments, some or all of the functionality of the exemplary baseband processor may be included in modules stored in memory 918 and executed via a central processing unit (CPU 914). The radio control functions may include, but are not limited to, signal modulation/demodulation, encoding/decoding, radio frequency shifting, and the like. In some embodiments, the modulation/demodulation circuitry of the baseband circuitry 904 may include Fast Fourier Transform (FFT), precoding, or constellation mapping/demapping functionality. In some embodiments, the encoding/decoding circuitry of baseband circuitry 904 may include convolutional, tail-biting convolutional, turbo, viterbi, or Low Density Parity Check (LDPC) encoder/decoder functionality. Embodiments of the modulation/demodulation and encoder/decoder functions are not limited to these examples, and other suitable functions may be included in other embodiments.

In some embodiments, the baseband circuitry 904 may include a Digital Signal Processor (DSP), such as one or more audio DSPs 916. The one or more audio DSPs 916 may include elements for compression/decompression and echo cancellation, and may include other suitable processing elements in other embodiments. In some embodiments, the components of the baseband circuitry may be combined in a single chip, a single chipset, or disposed on the same circuit board, as appropriate. In some embodiments, some or all of the constituent components of the baseband circuitry 904 and the application circuitry 902 may be implemented together, such as on a system on a chip (SOC).

In some implementations, the baseband circuitry 904 may provide communications compatible with one or more radio technologies. For example, in some embodiments, baseband circuitry 904 may support communication with an Evolved Universal Terrestrial Radio Access Network (EUTRAN) or other Wireless Metropolitan Area Network (WMAN), Wireless Local Area Network (WLAN), Wireless Personal Area Network (WPAN). Embodiments in which the baseband circuitry 904 is configured to support radio communications of more than one wireless protocol may be referred to as multi-mode baseband circuitry.

Rf circuit 920 may enable communication with a wireless network through a non-solid medium using modulated electromagnetic radiation. In various implementations, the RF circuitry 920 may include switches, filters, amplifiers, and the like to facilitate communication with the wireless network. RF circuitry 920 may include a receive signal path that may include circuitry to down-convert RF signals received from FEM circuitry 930 and provide baseband signals to baseband circuitry 904. The RF circuitry 920 may also include a transmit signal path, which may include circuitry to upconvert baseband signals provided by the baseband circuitry 904 and provide an RF output signal for transmission to the FEM circuitry 930.

In some embodiments, the receive signal path of RF circuit 920 may include a mixer circuit 922, an amplifier circuit 924, and a filter circuit 926. In some implementations, the transmit signal path of the RF circuitry 920 may include filter circuitry 926 and mixer circuitry 922. The RF circuit 920 may also include a synthesizer circuit 928 to synthesize frequencies for use by the mixer circuits 922 for the receive and transmit signal paths. In some embodiments, the mixer circuit 922 of the receive signal path may be configured to down-convert RF signals received from the FEM circuit 930 based on a synthesis frequency provided by the synthesizer circuit 928. The amplifier circuit 924 may be configured to amplify the downconverted signal, and the filter circuit 926 may be a Low Pass Filter (LPF) or a Band Pass Filter (BPF) configured to remove unwanted signals from the downconverted signal to generate an output baseband signal. The output baseband signal may be provided to baseband circuitry 904 for further processing. In some embodiments, the output baseband signal may be a zero frequency baseband signal, although this is not required. In some embodiments, mixer circuit 922 of the receive signal path may comprise a passive mixer, although the scope of the embodiments is not limited in this respect.

In some embodiments, the mixer circuitry 922 of the transmit signal path may be configured to upconvert an input baseband signal based on a synthesis frequency provided by the synthesizer circuitry 928 to generate an RF output signal for the FEM circuitry 930. The baseband signal may be provided by baseband circuitry 904 and may be filtered by filter circuitry 926.

In some embodiments, the mixer circuit 922 of the receive signal path and the mixer circuit 922 of the transmit signal path may comprise two or more mixers and may be arranged for quadrature down-conversion and up-conversion, respectively. In some embodiments, the mixer circuit 922 of the receive signal path and the mixer circuit 922 of the transmit signal path may include two or more mixers and may be arranged for image rejection (e.g., Hartley image rejection). In some embodiments, the mixer circuit 922 and the mixer circuit 922 of the receive signal path may be arranged for direct down-conversion and direct up-conversion, respectively. In some embodiments, the mixer circuit 922 of the receive signal path and the mixer circuit 922 of the transmit signal path may be configured for superheterodyne operation.

In some embodiments, the output baseband signal and the input baseband signal may be analog baseband signals, although the scope of the embodiments is not limited in this respect. In some alternative embodiments, the output baseband signal and the input baseband signal may be digital baseband signals. In these alternative embodiments, RF circuitry 920 may include analog-to-digital converter (ADC) and digital-to-analog converter (DAC) circuitry, and baseband circuitry 904 may include a digital baseband interface to communicate with RF circuitry 920.

In some dual-mode embodiments, separate radio IC circuits may be provided to process signals for each spectrum, although the scope of the embodiments is not limited in this respect.

In some embodiments, synthesizer circuit 928 may be a fractional-N synthesizer or a fractional N/N +1 synthesizer, although the scope of embodiments is not limited in this respect as other types of frequency synthesizers may also be suitable. For example, synthesizer circuit 928 may be a delta-sigma synthesizer, a frequency multiplier, or a synthesizer including a phase locked loop with a frequency divider.

The synthesizer circuit 928 may be configured to synthesize an output frequency based on the frequency input and the divider control input for use by the mixer circuit 922 of the RF circuit 920. In some embodiments, the synthesizer circuit 928 may be a fractional N/N +1 synthesizer.

In some embodiments, the frequency input may be provided by a Voltage Controlled Oscillator (VCO), although this is not required. The divider control input may be provided by either baseband circuitry 904 or application circuitry 902 (such as an application processor) depending on the desired output frequency. In some implementations, the divider control input (e.g., N) can be determined from a look-up table based on the channel indicated by the application circuitry 902.

The synthesizer circuit 928 of the RF circuit 920 may include a frequency divider, a Delay Locked Loop (DLL), a multiplexer, and a phase accumulator. In some embodiments, the frequency divider may be a dual-mode frequency divider (DMD) and the phase accumulator may be a Digital Phase Accumulator (DPA). In some embodiments, the DMD may be configured to divide an input signal by N or N +1 (e.g., based on a carry) to provide a fractional division ratio. In some example embodiments, a DLL may include a cascaded, tunable, delay element, a phase detector, a charge pump, and a D-type flip-flop set. In these embodiments, the delay elements may be configured to divide the VCO period into Nd equal phase groups, where Nd is the number of delay elements in the delay line. Thus, the DLL provides negative feedback to help ensure that the total delay through the delay line is one VCO cycle.

In some embodiments, the synthesizer circuit 928 may be configured to generate a carrier frequency as the output frequency, while in other embodiments the output frequency may be a multiple of the carrier frequency (e.g., twice the carrier frequency, four times the carrier frequency) and may be used with a quadrature generator and divider circuit to generate multiple signals at the carrier frequency with multiple different phases relative to each other. In some implementations, the output frequency may be the LO frequency (fLO). In some embodiments, the RF circuitry 920 may include an IQ/polarity converter.

FEM circuitry 930 may include a receive signal path that may include circuitry configured to operate on RF signals received from one or more antennas 932, amplify the received signals, and provide amplified versions of the received signals to RF circuitry 920 for further processing. FEM circuitry 930 may also include a transmit signal path, which may include circuitry configured to amplify transmit signals provided by RF circuitry 920 for transmission by one or more of the one or more antennas 932. In various implementations, amplification through the transmit or receive signal path may be accomplished only in the RF circuitry 920, only in the FEM circuitry 930, or both the RF circuitry 920 and the FEM circuitry 930.

In some implementations, the FEM circuitry 930 may include TX/RX switches to switch between transmit mode and receive mode operation. The FEM circuitry 930 may include a receive signal path and a transmit signal path. The receive signal path of FEM circuitry 930 may include an LNA to amplify the received RF signal and provide the amplified received RF signal as an output (e.g., to RF circuitry 920). The transmit signal path of FEM circuitry 930 may include a Power Amplifier (PA) to amplify an input RF signal (e.g., provided by RF circuitry 920), and one or more filters to generate an RF signal for subsequent transmission (e.g., by one or more of the one or more antennas 932).

In some embodiments, PMC 934 may manage power provided to baseband circuitry 904. In particular, the PMC 934 may control power selection, voltage scaling, battery charging, or DC-DC conversion. The PMC 934 may generally be included when the device 900 is capable of being battery powered, for example, when the device 900 is included in a UE. PMC 934 may improve power conversion efficiency while providing desired implementation size and heat dissipation characteristics.

Figure 9 shows PMC 934 coupled only to baseband circuitry 904. However, in other embodiments, PMC 934 may additionally or alternatively be coupled with other components (such as, but not limited to, application circuitry 902, RF circuitry 920, or FEM circuitry 930) and perform similar power management operations for these components.

In some embodiments, PMC 934 may control or otherwise be part of various power saving mechanisms of device 900. For example, if the device 900 is in an RRC _ Connected state, where the device is still Connected to the RAN node because it expects to receive traffic immediately, after a period of inactivity, the device may enter a state referred to as discontinuous reception mode (DRX). During this state, the device 900 may be powered down for short time intervals, thereby saving power.

If there is no data traffic activity for an extended period of time, the device 900 may transition to an RRC _ Idle state, where the device is disconnected from the network and no operations such as channel quality feedback, handover, etc. are performed. The device 900 enters a very low power state and performs paging, where the device again periodically wakes up to listen to the network and then powers down again. Device 900 is unable to receive data in this state and, in order to receive data, the device must transition back to the RRC Connected state.

The additional power-save mode may cause the device to be unavailable to the network for longer than the paging interval (ranging from a few seconds to a few hours). During this time, the device is completely unable to connect to the network and can be completely powered down. Any data transmitted during this period will cause significant delay and the delay is assumed to be acceptable.

A processor of the application circuitry 902 and a processor of the baseband circuitry 904 may be used to execute elements of one or more instances of a protocol stack. For example, a processor of the baseband circuitry 904 may be used, alone or in combination, to perform layer 3, layer 2, or layer 1 functions, while a processor of the application circuitry 902 may utilize data (e.g., packet data) received from these layers and further perform layer 4 functions (e.g., Transmission Communication Protocol (TCP) and User Datagram Protocol (UDP) layers). As mentioned herein, layer 3 may include a Radio Resource Control (RRC) layer, described in further detail below. As mentioned herein, layer 2 may include a Medium Access Control (MAC) layer, a Radio Link Control (RLC) layer, and a Packet Data Convergence Protocol (PDCP) layer, as described in further detail below. As mentioned herein, layer 1 may comprise the Physical (PHY) layer of the UE/RAN node, as described in further detail below.

Fig. 10 illustrates an exemplary interface 1000 of a baseband circuit according to some embodiments. As described above, the baseband circuitry 904 of fig. 9 may include a 3G baseband processor 906, a 4G baseband processor 908, a 5G baseband processor 910, other baseband processors 912, a CPU 914, and a memory 918 for use by the processors. As shown, each of these processors may include a respective memory interface 1002 to send/receive data to/from memory 918.

The baseband circuitry 904 may also include one or more interfaces to communicatively couple to other circuitry/devices, such as a memory interface 1004 (e.g., an interface to send/receive data to/from memory external to the baseband circuitry 904), an application circuitry interface 1006 (e.g., an interface to send/receive data to/from the application circuitry 902 of fig. 9), an RF circuitry interface 1008 (e.g., an interface to send/receive data to/from the RF circuitry 920 of fig. 9), a wireless hardware connection interface 1010 (e.g., an interface to send/receive data to/from a Near Field Communication (NFC) component, a wireless communication link, a wireless,

The components (e.g.,

low power consumption),

Interfaces for components and other communicating components to send/receive data) and a power management interface 1012 (e.g., an interface for sending/receiving power or control signals to/from PMC 934).

Fig. 11 is a block diagram illustrating components of a system 1100 that supports NFV, according to some example embodiments. System 1100 is shown to include a virtualization infrastructure manager (shown as VIM 1102), a network function virtualization infrastructure (shown as NFVI 1104), a VNF manager (shown as VNFM 1106), a virtualized network function (shown as VNF 1108), an element manager (shown as EM 1110), a NFV coordinator (shown as NFVO 1112), and a network manager (shown as NM 1114).

VIM 1102 manages the resources of NFVI 1104. NFVI 1104 may include physical or virtual resources and applications (including hypervisors) for executing system 1100. VIM 1102 can utilize NFVI 1104 to manage the lifecycle of virtual resources (e.g., creation, maintenance, and teardown of Virtual Machines (VMs) associated with one or more physical resources), track VM instances, track performance, failure, and security of VM instances and associated physical resources, and expose VM instances and associated physical resources to other management systems.

VNFM 1106 may manage VNF 1108. VNF 1108 may be used to perform EPC components/functions. VNFM 1106 may manage the lifecycle of VNF 1108 and track performance, failure, and security of VNF 1108 in terms of virtualization. EM 1110 may track performance, failure, and security of VNF 1108 in terms of functionality. The tracking data from VNFM 1106 and EM 1110 may include, for example, Performance Measurement (PM) data used by VIM 1102 or NFVI 1104. Both VNFM 1106 and EM 1110 may scale up/down the number of VNFs of system 1100.

NFVO 1112 may coordinate, authorize, release, and engage NFVI 1104 resources to provide requested services (e.g., perform EPC functions, components, or slices). NM 1114 may provide an end-user functionality grouping responsible for network management, possibly including network elements with VNFs, non-virtualized network functions, or both (management of VNFs may occur via EM 1110).

Fig. 12 is a block diagram illustrating components 1200 capable of reading instructions from a machine-readable or computer-readable medium (e.g., a non-transitory machine-readable storage medium) and of performing any one or more of the methodologies discussed herein, according to some example embodiments. In particular, fig. 12 shows a schematic diagram of hardware resources 1202, including one or more processors 1212 (or processor cores), one or more memory/storage devices 1218, and one or more communication resources 1220, each of which may be communicatively coupled via a bus 1222. For embodiments in which node virtualization (e.g., NFV) is utilized, hypervisor 1204 may be executed to provide an execution environment for one or more network slices/subslices to utilize hardware resources 1202.

Processor 1212 (e.g., a Central Processing Unit (CPU), a Reduced Instruction Set Computing (RISC) processor, a Complex Instruction Set Computing (CISC) processor, a Graphics Processing Unit (GPU), a Digital Signal Processor (DSP) such as a baseband processor, an Application Specific Integrated Circuit (ASIC), a Radio Frequency Integrated Circuit (RFIC), another processor, or any suitable combination thereof) may include, for example, processor 1214 and processor 1216.

The memory/storage device 1218 may include main memory, disk storage, or any suitable combination thereof. The memory/storage 1218 may include, but is not limited to, any type of volatile or non-volatile memory, such as Dynamic Random Access Memory (DRAM), Static Random Access Memory (SRAM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), flash memory, solid state memory, and the like.

The communication resources 1220 may include interconnection or network interface components or other suitable devices to communicate with one or more peripheral devices 1206 or one or more databases 1208 via the network 1210. For example, the communication resources 1220 can include wired communication components (e.g., for coupling via a Universal Serial Bus (USB)), cellular communication components, NFC components, and/or the like,

The components (e.g.,

low power consumption),

Components and other communication components.

The instructions 1224 may include software, a program, an application, an applet, an application, or other executable code for causing at least any one of the processors 1212 to perform any one or more of the methodologies discussed herein. The instructions 1224 may reside, completely or partially, within at least one of the processors 1212 (e.g., within a cache memory of the processor), the memory/storage 1218, or any suitable combination thereof. Further, any portion of the instructions 1224 may be communicated to the hardware resources 1202 from any combination of the peripheral devices 1206 or the database 1208. Thus, the memory of the processor 1212, the memory/storage 1218, the peripherals 1206, and the database 1208 are examples of computer-readable and machine-readable media.

For one or more embodiments, at least one of the components illustrated in one or more of the foregoing figures may be configured to perform one or more operations, techniques, processes, and/or methods as described in the examples section below. For example, the baseband circuitry described above in connection with one or more of the preceding figures may be configured to operate in accordance with one or more of the following embodiments. As another example, circuitry associated with a UE, base station, network element, etc., as described above in connection with one or more of the preceding figures, can be configured to operate in accordance with one or more of the embodiments illustrated below in the embodiments section.

Examples section

The following examples relate to further embodiments.

Embodiment 1 is an apparatus for a User Equipment (UE) configured for multi-antenna communication. The apparatus includes a memory interface and a processor. The memory interface is to: communication data associated with a plurality of packets communicated using device-to-device (D2D) communication is sent to or received from a memory device. The processor is configured to: estimating at least one of a rank indicator and a channel quality indicator for the D2D communication based on the communication data and without using a dedicated reference signal for the D2D communication; and encoding a feedback message to one or more transmitters participating in the D2D communication, the feedback message indicating at least one of the rank indicator and the channel quality indicator.

Embodiment 2 is the apparatus of embodiment 1, wherein the UE is configured to function as at least one of a transmitter (Tx) and a receiver (Rx) for vehicle-to-all (V2X) communication.

Embodiment 3 is the apparatus of embodiment 1, wherein the communication data comprises hybrid automatic repeat request (HARQ) information including Acknowledgement (ACK) responses and Negative Acknowledgement (NACK) responses associated with the plurality of packets.

Embodiment 4 is the apparatus of embodiment 3, wherein the processor is further configured to: monitoring the ACK response and the NACK response for a selected modulation coding scheme; adjusting the modulation coding scheme to reduce the number of bits per symbol if the NACK response increases over a period of time; adjusting the modulation coding scheme to increase the number of bits per symbol if the NACK response decreases by or below a threshold amount within the time period; and encode the feedback message to include an indication of the adjustment to the modulation coding scheme.

Embodiment 5 is the apparatus of embodiment 1, wherein adjusting the modulation coding scheme comprises adjusting the modulation coding scheme only once every X received ACK/NACK responses.

Embodiment 6 is the apparatus of embodiment 1, wherein the communication data includes demodulation information associated with demodulation of the plurality of packets received at the UE using the D2D communication over a period of time.

Embodiment 7 is the apparatus of embodiment 6, wherein the demodulation information comprises a demodulation reference signal (DMRS).

Embodiment 8 is the apparatus of embodiment 7, wherein the processor is further configured to: determining an estimated channel to demodulate the plurality of packets based on the DMRS; and calculating the channel quality indicator based on long-term statistics of the estimated channel.

Embodiment 9 is the apparatus of embodiment 8, wherein the processor is further configured to: determining an interference measurement for each subchannel based on the DMRS; and determining the channel quality indicator by averaging or weighting both the estimated channel and the interference measurement over at least one of the time period and a bandwidth used for transmission.

Embodiment 10 is the apparatus of embodiment 8, wherein the processor is further configured to estimate the rank indicator based on the long-term statistics of the estimated channel.

Embodiment 11 is the apparatus of embodiment 10, wherein the processor is further configured to: configure the UE to use a single spatial layer for the D2D communication if channel coefficients received at different receive antennas of the UE corresponding to the same subcarriers and Orthogonal Frequency Division Multiplexing (OFDM) symbols are highly correlated; and if the channel coefficients are weakly correlated, configuring the UE to use multiple spatial layers for the D2D communication.

Embodiment 12 is the apparatus of embodiment 1, wherein the processor is further configured to: exchanging codebook information with one or more transmitters or receivers in communication with the UE using the D2D communication, the codebook information indicating a cycling of precoders for the plurality of packets; estimating a multiple-input multiple-output (MIMO) channel based on the cycling of the precoder; and determining the rank indicator based on the MIMO channel.

Embodiment 13 is a non-transitory computer-readable storage medium. The computer-readable storage medium includes instructions that, when executed by a baseband processor of a vehicle-to-all (V2X) device, cause the baseband processor to: estimating at least one of a rank indicator and a channel quality indicator for the D2D communication based on communication data associated with a plurality of packets transmitted using device-to-device (D2D) communications and without using a dedicated reference signal for the D2D communication; and encoding a feedback message to one or more transmitters engaged in communications using the D2D, the feedback message indicating at least one of the rank indicator and the channel quality indicator.

Embodiment 14 is the computer-readable storage medium of embodiment 13, wherein the communication data includes hybrid automatic repeat request (HARQ) information including Acknowledgement (ACK) responses and Negative Acknowledgement (NACK) responses associated with the transmitted plurality of packets.

Embodiment 15 is the computer-readable storage medium of embodiment 14, wherein the instructions further configure the baseband processor to: monitoring the ACK response and the NACK response for a selected modulation coding scheme; adjusting the modulation coding scheme to reduce the number of bits per symbol if the NACK response increases over a period of time; adjusting the modulation coding scheme to increase the number of bits per symbol if the NACK response decreases by or below a threshold amount within the time period; and encode the feedback message to include an indication of the adjustment to the modulation coding scheme.

Embodiment 16 is the apparatus of embodiment 15, wherein adjusting the modulation coding scheme comprises adjusting the modulation coding scheme only once every X received ACK/NACK responses.

Embodiment 17 is the computer-readable storage medium of embodiment 13, wherein the communication data includes demodulation information associated with demodulation of the plurality of packets received at the V2X device over a period of time.

Embodiment 18 is the computer-readable storage medium of embodiment 17, wherein the demodulation information comprises a demodulation reference signal (DMRS).

Embodiment 19 is the computer-readable storage medium of embodiment 18, wherein the instructions further configure the baseband processor to: determining an estimated channel to demodulate the plurality of packets based on the DMRS; and calculating the channel quality indicator based on long-term statistics of the estimated channel.

Embodiment 20 is the computer-readable storage medium of embodiment 19, wherein the instructions further configure the baseband processor to: determining an interference measurement for each subchannel based on the DMRS; and determining the channel quality indicator by averaging or weighting both the estimated channel and the interference measurement over at least one of the time period and a bandwidth used for transmission.

Embodiment 21 is the computer-readable storage medium of embodiment 19, wherein the instructions further configure the baseband processor to: estimating the rank indicator based on the long-term statistics of the estimated channel.

Embodiment 21 is the computer-readable storage medium of embodiment 20, wherein the instructions further configure the baseband processor to: configure the UE to use a single spatial layer for the D2D communication if channel coefficients received at different receive antennas of the V2X device corresponding to the same subcarriers and Orthogonal Frequency Division Multiplexing (OFDM) symbols are highly correlated; and if the channel coefficients are weakly correlated, configuring the V2X device to use multiple spatial layers for the D2D communication.

Embodiment 23 is the computer-readable storage medium of embodiment 13, wherein the instructions further configure the baseband processor to: exchanging codebook information with one or more transmitters or receivers in communication with the V2X device, the codebook information indicating a cycle of precoders for the plurality of packets; estimating a multiple-input multiple-output (MIMO) channel based on the cycling of the precoder; and determining the rank indicator based on the MIMO channel.

Any of the above embodiments may be combined with any other embodiment (or combination of embodiments) unless explicitly stated otherwise. The foregoing description of one or more specific implementations provides illustration and description, but is not intended to be exhaustive or to limit the scope of the embodiments to the precise form disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practice of various embodiments.

Embodiments and implementations of the systems and methods described herein may include various operations that may be embodied in machine-executable instructions to be executed by a computer system. The computer system may include one or more general purpose or special purpose computers (or other electronic devices). The computer system may include hardware components that include specific logic components for performing operations, or may include a combination of hardware, software, and/or firmware.

It should be appreciated that the system described herein includes descriptions of specific embodiments. The embodiments may be combined into a single system, partially incorporated into other systems, divided into multiple systems, or otherwise divided or combined. Furthermore, it is contemplated that parameters/attributes/aspects, etc. of one embodiment may be used in another embodiment. For clarity, these parameters/properties/aspects, etc. have been described in one or more embodiments only, and it should be recognized that these parameters/properties/aspects, etc. may be combined with or substituted for parameters/properties, etc. of another embodiment unless specifically stated herein.

Although the foregoing has been described in some detail for purposes of clarity of understanding, it will be apparent that certain changes and modifications may be made without departing from the principles of the invention. It should be noted that there are many alternative ways of implementing both the processes and apparatuses described herein. Accordingly, the present embodiments are to be considered as illustrative and not restrictive, and the description is not to be limited to the details given herein, but may be modified within the scope and equivalents of the appended claims.

Claims (23)

1. An apparatus for a User Equipment (UE) configured for multi-antenna communication, the apparatus comprising:

a memory interface to: sending or receiving communication data associated with a plurality of packets communicated using device-to-device (D2D) communications to or from a memory device; and

a processor to:

estimating at least one of a rank indicator and a channel quality indicator for the D2D communication based on the communication data and without using a dedicated reference signal for the D2D communication; and

encoding a feedback message to one or more transmitters participating in the D2D communication, the feedback message indicating at least one of the rank indicator and the channel quality indicator.

2. The apparatus of claim 1, wherein the UE is configured as at least one of a transmitter (Tx) and a receiver (Rx) for vehicle-to-all (V2X) communication.

3. The apparatus of claim 1, wherein the communication data comprises hybrid automatic repeat request (HARQ) information comprising Acknowledgement (ACK) responses and Negative Acknowledgement (NACK) responses associated with the plurality of packets.

4. The apparatus of claim 3, wherein the processor is further configured to:

monitoring the ACK response and the NACK response for a selected modulation coding scheme;

adjusting the modulation coding scheme to reduce the number of bits per symbol if the NACK response increases over a certain period of time;

adjusting the modulation coding scheme to increase the number of bits per symbol if the NACK response decreases by or below a threshold number within the time period; and

encoding the feedback message to include an indication to adjust the modulation coding scheme.

5. The apparatus of claim 1, wherein adjusting the modulation coding scheme comprises: the modulation coding scheme is adjusted only once per X received ACK/NACK responses.

6. The apparatus of claim 1, wherein the communication data comprises demodulation information associated with demodulation of the plurality of packets received at the UE using the D2D communication over a certain time period.

7. The apparatus of claim 6, wherein the demodulation information comprises a demodulation reference signal (DMRS).

8. The apparatus of claim 7, wherein the processor is further configured to:

determining an estimated channel to demodulate the plurality of packets based on the DMRS; and

calculating the channel quality indicator based on long-term statistics of the estimated channel.

9. The apparatus of claim 8, wherein the processor is further configured to:

determining an interference measurement for each subchannel based on the DMRS; and

determining the channel quality indicator by averaging or weighting both the estimated channel and the interference measurement over at least one of the time period and a bandwidth used for transmission.

10. The apparatus of claim 8, wherein the processor is further configured to estimate the rank indicator based on the long-term statistics of the estimated channel.

11. The apparatus of claim 10, wherein the processor is further configured to:

configure the UE to use a single spatial layer for the D2D communication if channel coefficients received at different receive antennas of the UE corresponding to the same subcarriers and Orthogonal Frequency Division Multiplexing (OFDM) symbols are highly correlated; and

configuring the UE to use multiple spatial layers for the D2D communication if the channel coefficients are weakly correlated.

12. The apparatus of claim 1, wherein the processor is further configured to:

exchanging codebook information with one or more transmitters or receivers in communication with the UE using the D2D communication, the codebook information indicating a cycling of precoders for the plurality of packets;

estimating a multiple-input multiple-output (MIMO) channel based on the cycling of the precoder; and

determining the rank indicator based on the MIMO channel.

13. A non-transitory computer-readable storage medium comprising instructions that, when executed by a baseband processor of a vehicle-to-all (V2X) device, cause the baseband processor to:

estimating at least one of a rank indicator and a channel quality indicator for the D2D communication based on communication data associated with a plurality of packets transmitted using device-to-device (D2D) communications and without using a dedicated reference signal for the D2D communication; and

encoding a feedback message to one or more transmitters engaged in communication using the D2D, the feedback message indicating at least one of the rank indicator and the channel quality indicator.

14. The computer-readable storage medium of claim 13, wherein the communication data comprises hybrid automatic repeat request (HARQ) information including Acknowledgement (ACK) responses and Negative Acknowledgement (NACK) responses associated with the transmitted plurality of packets.

15. The computer-readable storage medium of claim 14, wherein the instructions further configure the baseband processor to:

monitoring the ACK response and the NACK response for a selected modulation coding scheme;

adjusting the modulation coding scheme to reduce the number of bits per symbol if the NACK response increases over a certain period of time;

adjusting the modulation coding scheme to increase the number of bits per symbol if the NACK response decreases by or below a threshold number within the time period; and

encoding the feedback message to include an indication to adjust the modulation coding scheme.

16. The apparatus of claim 15, wherein adjusting the modulation coding scheme comprises: the modulation coding scheme is adjusted only once per X received ACK/NACK responses.

17. The computer-readable storage medium of claim 13, wherein the communication data includes demodulation information associated with demodulation of the plurality of packets received at the V2X device over a period of time.

18. The computer-readable storage medium of claim 17, wherein the demodulation information comprises a demodulation reference signal (DMRS).

19. The computer-readable storage medium of claim 18, wherein the instructions further configure the baseband processor to:

determining an estimated channel to demodulate the plurality of packets based on the DMRS; and

calculating the channel quality indicator based on long-term statistics of the estimated channel.

20. The computer-readable storage medium of claim 19, wherein the instructions further configure the baseband processor to:

determining an interference measurement for each subchannel based on the DMRS; and

determining the channel quality indicator by averaging or weighting both the estimated channel and the interference measurement over at least one of the time period and a bandwidth used for transmission.

21. The computer-readable storage medium of claim 19, wherein the instructions further configure the baseband processor to: estimating the rank indicator based on the long-term statistics of the estimated channel.

22. The computer-readable storage medium of claim 20, wherein the instructions further configure the baseband processor to:

configure the UE to use a single spatial layer for the D2D communication if channel coefficients received at different receive antennas of the V2X device corresponding to the same subcarriers and Orthogonal Frequency Division Multiplexing (OFDM) symbols are highly correlated; and

configuring the V2X device to use multiple spatial layers for the D2D communication if the channel coefficients are weakly correlated.

23. The computer-readable storage medium of claim 13, wherein the instructions further configure the baseband processor to:

exchanging codebook information with one or more transmitters or receivers in communication with the V2X device, the codebook information indicating a cycle of precoders for the plurality of packets;

estimating a multiple-input multiple-output (MIMO) channel based on the cycling of the precoder; and

determining the rank indicator based on the MIMO channel.

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